Apparatus for drying filmlike materials



C. N. EDWARDS APPARATUS FOR DRYING FILMLIKE mmms July 14, 1953 FiledFeb. 7, 1950 grwe/wkw CHARLES M EDWARDS July 14, 1953 c. N. EDWARDSAPPARATUS FOR DRYING FILMLIKE-MATERIALS 2 Shoots-8218M -2 Filed Feb. 7,1950 FIG. 4

Swot rm 'G'HARLES' N. EDWARDS Patented July 14, i953 UNITED STATESPATENT or Flea;

. g 2,645,031 a 1 APPARATUS FOR DRYING FILMLIKE MATERIALS 7 Charles N.Edwards,'Washington, D. 0., assignor to Hispeed Equipment, Inc., NewYork, N. Y., a V corporation of New York Application February 7, 1950,Serial No. 142,862

4 Claims. (Cl. 34' 48) (Granted under Title 35, U. s. Code (1952), I

sec. 266) 1 This invention relates to a method and apparatus for dryingplastics, paper, fabrics and the like. In particular, it relates toapparatus for rapidly drying moist plastic or'otherwise non- 2. andconverted to heat ,by silver or other metal particles present in thecoating or support in direct proportion to theamount of metallicparticles present.

rigid, permeable or non-permeable films or sup- 5 The disadvantages ofthe prior art apparatus ports which may be coated or uncoated and are inwhich the drying operation is controlled by moist orin thoroughly soakedcondition. any of the above described methods lie in the Existingapparatus and methods for accom-- disproportionately large and bulkyequipment replishing this accelerated drying generally involve quired,the power required .tooperate the moving a relatively large dryingchamber in which the parts and to produce heat or radiant energy andplastic, e. g. the film and its support, is passed the cost ofmaintaining chemical or-physical dryover a series of drums and issubjected to the ing agents. Large volumesof .dried air areredesiccating action of heated air passing through quired and whereverspeed of drying is critical, the chamber. The method, when acceleratedexcessively dry and hotair must be useda.condrying'is desired, generallyincludes the pre1im-- dition which tends to producefilm brittleness andinary step or removal of all liquids or solutions scorching andthesetting' up ofv internal strains which may be on the outer surfacesofthe film in the film base with resultant image distortion or support.This step is followed by the removal and dimensional instability. ofwater which may be'in the pore or interstitial It is therefore thegeneral object of the invenspaces in the film and the support. This steption to provide apparatus for the rapid. drying is accomplished by adrying atmosphere which of film like materialor supports 'whichis commaybe warmed or heated dry air. pact and of relatively small overalldimensions.

As is well known, the air for the drying of the It isalso an object ofvthe invention to provide film or support may be conditioned for rapiddryapparatus'for drying plastic film structures and ing in any one ofthe three following ways: the like wherein the upper and lower surfacesof 1. The air to be used may be cooled to a'temthe film structure arebathed in a rapidly moving perature below its dewpoint, which results inthe current of compressed air at ambient or relatively condensation andprecipitation of the moisture in low temperature. 7 excess of thecarrying capacity at that tempera- 7 It is a further object of theinvention to provide ture. The air may then be heated to ambient 3capparatus for the drying of plastic film structemperature or abovethereby greatly increasing tures and'the like whereinthe film structureis its evaporative capacity. moved through the apparatus bythefrictional 2. The air to be used may be merely heated, contact of theair stream with the surfaces of thereby being expanded, the relativeproportion the film structure. of liquid vapor per unit volume beingthereby It is an additional object of the invention to decreased with aconsequent increase in evaporaprovide apparatus for the drying ofplastic film tive capacity. Furthermore, heating. the drying structuresand the like wherein the film strucair also accelerates the molecular'co-mingling ture in passing therethrough is subjected to high of theliquid and the air molecules thus accelerfrequency vibration such'assonic and ultrasonic ating thedrying action. 40 for the purpose ofincreasing the rate of re- 3. The air to be used may be dried by passagemoval and evaporation of the interstitial liquid. through a hygroscopicmaterial such-as activated It'is a specific object of the invention topro silica gel, calcium chloride or sulphuric acid, vide apparatus forthe rapid drying of photowhich may react chemically or physically toregraphic film. move the liquid vapor from the air. It is a furtherobject of the invention to pro- The drying of the filmor support mayalso be vide apparatus for the rapid drying; of film-like accelerated bythe application of energy in the structures in which there are nomechanically form of heat to the film or support to quicken movingparts. I q p the molecular activity of the;liquid contained 7 Otherobjectives such as economical cost of therein and thus increase itsvapor tension and Q manufacture of the apparatus, sturdiness of contherate of evaporation. The film or support may struction, etc., will beapparent: from the followbe heated by contact with a heated drum or ingdescription and the drawings hereto apother similar device. Alsoinfrared light may pended. I I be successfully used in drying of filmcoatings, The attainmentof these objectiveswith the the energy of theinfra red-ray beingabsorbed overcoming of the-disadvantages of-the priorart apparatus is accomplished by the relatively simple apparatus of thisinvention to be described hereinafter and illustrated in preferredembodiments in the accompanying drawings wherein the same' referencecharacters in the different figures designate the same elements andwherein Fig. 1 is an isometric view, partly cut away, of a simple formof the invention showing the film in drying position in the dryingpassageway.

Fig. 2 is a longitudinal vertical cross section taken along thelongitudinal center line of Fig. 1 showing the relationship of thecompressed air inlets and the vertical tapering of the dryingpassageway.

Fig. 3 is a side elevation in exploded form of V a larger embodiment ofthe invention.

Fig. 4 is a top plan view of the upper member of the apparatus showing apreferred configuration of the air chamber.

Fig. 5 is an end elevation, in exploded form, of this larger embodimentshowing particularly the lateral dovetailing construction of the upperand lower members.

Fig. 6 is a longitudinal section taken through an embodiment of theinvention of the type illustrated in Figs. 3, 4 and 5.

In Fig. 1 the drying apparatus is shown generally at [0. The apparatusherein shown in its simplest embodiment comprises an upper member I2 anda lower member 14 which may be fastened together by any suitable meanssuch as machine screws IS. The abutting faces of these two members maybe cut away or formed as at [8 and in Fig. 2 to constitute a passageway22 within and between these two members. This passageway may be taperedlongitudinally and vertically to provide a restriction 62 intermediatethe ends of the passageway from which two diffusers eminate. The tapermay be of the order of 1 in the vertical dimension of the passagewayincreasing both toward the feed end and the discharge end from a throatpoint within the passageway. The surface of passageway may beprotectively coated to prevent corrosive action by the photographicchemicals which may be carried in dilute solution by the liquid in andon the film structure. Compressed air inlet ducts are shown at 24 and26. These ducts are connected to a source of compressed air (not shown).At their discharge ends they fan out to the full width of the passagewayas shown in dash line at 28 and 30. These compressed air inletsdischarge air into the passageway in the form of sheets which may beoffset with respect to each other as shown in Fig. 2 at 32 and 34. Theeffect of the offsetting of the air inlets is that the film as its feedsinto the passageway is first bent upwardly by the blast of air comingfrom the lower inlet and then downwardly by the blast of air coming fromthe upper inlet. This continuous flexing of the film imparts a vibrationof very high frequency thereto which decreases in amplitude andfrequency as the film moves through the passageway. The effect of thisvibration on the rate of drying will be discussed hereinafter.

An embodiment of the invention for drying film structures of greaterwidth is shown in Figs. 3, 4 and 5. In Fig. 3 members 36 and 38 areshown as being provided with air chambers 40 and 42, respectively. Thefunction of these air chambers is to provide spaces in which the dryingair may be heated to a predetermined temperature in order to increasethe rate of drying without scorching or rendering the film brittle. Aconfiguration, which is preferred, of air chamber 40 is shown in Fig. 4.Top and bottom plates 44 and 46 are adapted to be firmly attached tomembers 36 and 38 by suitable means such as screws [6 which may extendthrough the top plate 44, members 36 and 38 and threadedly engage bottomplate 46. In Fig. 5 a suitable means of sealing passageway 22 laterallyis shown in the dovetail joints 48 and 50. Conduits for the introductionof dry compressed air into the air chamber are shown at 24 and 26. Asstated above these air chambers may be provided with electricallyoperated heating elements such as resistance wires or other means whichunder thermostatic control heat the incoming air to a desiredtemperature.

The sectional view shown by Fig. 6 illustrates the method of operationof this invention. Here wet film 60 with its support is fed into thefeed end of the drier into the restriction or throat 62 of passageway22.

Compressed dry air, flowing in the direction indicated by the arrows,enters air chambers 40 and 42 from conduits 24 and 26, respectively. Itpasses around and through electrical resistance coils 64 and 66 whichare controlled by preset thermostatic switches 68 and 10 and dischargesfrom these air chambers through ducts 4| and 43 into passageway 22. Theair from duct 43 impinges upon the film bending it upwardly. As the filmmoves forward compressed dry air from duct 4| impinges upon the uppersurface of film 60 bending it downwardly. As stated supra, because ofthis continual bending of the film in sequentially opposite directionsit is caused to vibrate at a very high frequency-as high as sonic andultrasonic depending on the physical characteristics of the filmstructure such as elasticity and stiffness, the relative positioning ofthe air inlet slots, and the air pressure.

A part of the air impinging on the film counterfiows out through theentrance sweeping the liquid adhering to both surfaces before it in atype of squeegee action. The film arriving at the throat of thepassageway is superficially dry.

The film is moved through the passageway by the frictional contact ofthe two opposed blasts of air with the surfaces of the film. As the filmmoves through the passageway it continues to vibrate in the form of asine wave but at a decreasing amplitude and frequency because of thedrop in air pressure. This high frequency vibration and flexing of thefilm has a peculiar effect on the liquid which may be present in thepore or interstitial spaces in the support and in the film itself if itis not impervious. Apparently, this rapid vibration causes the liquid tomove out to the surface from the interstitial spaces and to be rapidlyevaporated by the ambient dry air before leaving the exit end of thepassageway. In passing through the apparatus the film does not touch thesurfaces of the passageway at any point since it is cushioned andseparated therefrom on all sides by rapidly moving currents ofcompressed air. This prevents scratching and marring of the coated,developed surface of the film.

In comparative test runs the drier of this invention having overalldimensions of about 12 x 2" x 1" has thoroughly dried 16 mm. and 35 mm.film at the rate of 55 feet per minute as compared with about 5-10 feetper minute generally obtained by prior art equipment having a spacerequirement of about 15 cubic feet.

The embodiment shown in Figs, 3, 4 and 5, having overall dimensions ofabout 18" x x 2%" operating on dried air heated to about 100 F. hasthoroughly dried 10" film at the rate of 20 feet per minute as comparedwith about one foot per minute generally obtained in a prior art dryingchamber having a space requirement of about 10 cubic feet. The spaceeconomy for a much increased rate drying capacity and the efiiciency inoperation of this inventors apparatus is thus readily apparent.

While specific embodiments of the invention have been herein describedand disclosed in the drawings, it is not desired to be strictly limitedthereto since obviously one skilled in the art could make changes in theparticular structure disclosed, such as variation in the taper angle ofthe passageway, the configuration of the air chamber, the overalldimensions and means of fastening the component elements togetherWithout departing from the spirit and scope of the invention. Suchmodifications are included in the invention to the extent as defined bythe herewith appended claims.

The invention described herein may be manufactured and used by or forthe Govermnent of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. Apparatus for the rapid drying of plastic fihns and the like by themovement of said plastic films therethrough comprising a housing body, apassageway for the conduction of said plastic films extending centrallyand longitudinally through said body, conduit means in said body forintroducing into said passageway a gaseous drying medium under pressureto move 'forward said plastic films and the like in said passageway andto rapidly dry them therein, said housing comprising at least twomembers attached together with said passageway symmetrically positionedin and between said members, said passageway increasing in verticaldimension toward both the inlet and discharge ends from a throat pointtherein, said conduit means including at least one conduit in each ofsaid members for introducing into said passageway near said throat at aninclination in the direction of movement of the plastic films and thelike through said passageway a dried gaseous medium under pressure tomove said plastic films and the like through said passageway and torapidly dry them therein.

2. Apparatus as defined in claim 1 wherein the conduits as thereindefined are positioned in offset relationship with respect to each otherand with respect to the longitudinal dimension of said passageway.

3. Apparatus as defined in claim 1 wherein each of said memberscomprises an air heating chamber, said conduits being connected to saidchamber for the conduction of the gaseous drying medium therethroughprior to entry into said passageway, and thermostatically controlledelectrical heating means in said chamber for heating said gaseous dryingmedium as it is conducted therethrough.

4. Apparatus as defined in claim 1 wherein the conduits as thereindefined are positioned in offset relationship with respect to each otherand the longitudinal axis of said passageway in order to direct streamsof gaseous drying medium to impinge in offset relationship with respectto each other upon opposed surfaces of said plastic films whereby saidfilms are caused to vibrate at relatively high frequency and to be movedthrough said passageway.

CHARLES N. EDWARDS.

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